It has long been the practice to shield heat sources for the danger they may cause to equipment or the occupant of motor vehicles. For example, catalytic converters are shielded because of the high temperatures generated within the converter. Further sections of exhaust pipe are shielded to protect operators of motorcycles.
Fuel tanks have been shielded with various structures known in the prior art. Most of the structures known are metal plates of various forms which cover the fuel tank and may provide an air gap between the outside of the fuel tank and the shield. The benefits of this shield are particularly attractive for plastic gas tanks which have a lower melting point than metal. It is considered beneficial in the prior art to keep any potential flame away from the gas tank by providing a metal shield.
Heretofore, a number of such shielding devices are known in the prior art. A Japanese publication 57-201,721 to Nippon Oil KK describes for use with a banded fuel tank sheets of unvulcanised rubber including an inorganic filler disposed between the vehicle body and fuel tank for its excellent water resistance, durability and self-fire extinguishing properties.
European patent 288,587 assigned to Rhein-Conti-Kunst describes a multi layered tank for motor fuel made of at least two layers of plastic not firmly joined together and having there between a small air gap or insulating layer. The outer layer of plastic has high impact strength and toughness.
West German publication 2,340,257 describes a fuel tank mounted under the floor of a vehicle which has asbestos cladding on the side near the exhaust pipe. The underside of the tank is protected by metal cladding fitted to the tank during molding. The cladding is held at a space from the tank wall for extra protection.
Japanese publication 57-140,226 assigned to the Honda Motor Company describes a fuel tank main body covered by a heat resistant material with the outside of the heat resistant material covered by a heat reflecting shielding film. When the tank is heated to the heat resisting temperature or above, the heat insulating material constituting the outer layer of the main body is carbonized to form a carbonized layer at the outside surface of the main body.
U.S. Pat. No. 4,895,268 to Ford discloses a plastic fuel tank which has a integral shield mounted thereto. U.S. Pat. No. 4,909,530 describes a flame cut off plate disposed between an exhaust pipe and the side wall of the fuel tank. U.S. Pat. No. 4,930,811 describes a flame cutoff plate disposed between an exhaust pipe and side wall of the fuel tank. These three references assigned to the Ford Motor Company, Fuji Jukogyo Kabushiki Kaisha, and Fuji Jukogyo Kabushiki Kaisha respectively describe the use of a metal plate shield.
Other examples of metal shields are found in U.S. Pat. Nos. 3,963,087, 3,863,445 and 4,085,816 which represent various forms that heat shields may take. West German publication 3,701,723 describes an impact guard to protect a car fuel tank including a sheet metal dish closed on the side facing the fuel tank offering protection from collision.
Nowhere within the prior art known to applicant is there found a composite heat shield for use in conjunction with a heat sensitive device to protect the device from a heat source which may tend to damage or destroy the device during periods of extreme heat generation. Such a heat shield would prevent the majority of heat passing across to the heat sensitive device and would minimize the effect of direct flame thereupon.
Most of the prior art heat shields are made up of metal cladding which is expensive to manufacture and difficult to form into required shapes. Metal is also an excellent conductor of heat and although such a heat shield may be provided with insulation or be set at a gap from, for example, the fuel tank, the heat managing properties of such a shield may not be sufficient to prevent the heat adjacent the plastic fuel tank from rising to within a critical zone of its melting temperature.
It is therefore a object of this invention to provide a heat shield which is light, economical, and effective.
It is a further object of this invention to provide a heat shield which is molded from sheet molding compound which is resistant to roadwear and has a portion of the sheet molding compound covered with reflecting metal cladding having disposed between the sheet molding compound and the cladding high temperature resistant insulation for the portion of the shield which is coextensive with a heat source in use.
Further and other objects of the invention will become apparent to those skilled in the art when considering the following summary of the invention and the more detailed description of the preferred embodiments illustrated herein.